Dump body lifting mechanism



Jan. 24, 1939. 'F. BISZANTZ ET AL 2,144,828

DUMP BODY LIFTING MECHANISM.

Filed Nov. 19, 1936 3 Sheets-Sheet l .T'MWMA BISZANTZ, NET/II KING,

KEN FRED 291.4% 15M;

Jan. 24, 1939. F. BISZANTZ ET 'AL I DUMP BODY LIFTING' MECHANISM 5 Sheets-Sheet 2 7mm FRED BISZANTZ, KENNETHJIKING. .575 I s Q 7.

Filed NOV. '19, 1936 Jan. 24; 1939. F. BISZANTZ ET AL 7 2,144,823

DUMP BODY LIFTING' MECHANISM Filed Nov. '19, 1936 5 sheets-Sheet 5- FREDBISZANTZ m m5 I a m. M E. K. Y 5

Patented Jan. 24, 1939 "UNITED STATES PATENT OF-FH'IE DUMP BODY LIFTING MECHANISM "Application November 19, 1936, Serial No. 111,700

12 Claims.

This invention relates to-dump body lifting mechanisms,:and in particular, to such mechanisms having a variable mechanical advantage for applying a variable force ata variable lifting speed during the dumping operation.

One object of "this invention is to provide a lifting mechanism-fordump trucks employinga system of levers arranged to alter the mechanical advantage of the mechanism so as to apply a relatively large lifting force with a relatively low lifting speed at the start of the lifting operation, and culminating in a relatively smaller lifting force with a more rapid lifting speed-at the-end of the dumping operation.

Another object is to provide a dump body lifting mechanism'having a system of levers arranged to provide a short weight arm at the beginning of the dumping operation and increasing to a long weight arm at the endof the dumping operation, causing a very high lifting force to be applied initially at a low speed, and a relatively low lifting force to be applied finally at a high speed, so that the'high lifting force is applied when the center of gravity of the load is farthest from-the pivot of the body and the lighter liftingforce is applied when the center of gravity has approached a position toward the rear of the truck-and over'the body pivots.

Another object is to provide such a mechanism employing a hydraulic motor of comparatively low power for-exerting the lifting effect because of the arrangement providing a variable mechanical advantage'throughout the lifting' operation correspondingto variation in the loadrequired to be lifted.

Another object is to provide a lifting mechanism for a dump truck, wherein a system of levers is arranged to provide a fixed length force arm with a variable lengthweight arm so as to apply a short weight arm initially and along weight arm finally during the "dumping oper- 'ation.

In the'drawings:

Figure l is a side elevation, partlybroken away, of'a dump body lifting mechanism according to the present invention.

Figure 2 is .an enlarged. detail section of a portion of Figure 1, taken along the line 22 in Figure 3.

Figure 3 is a top'plan view of the dumping mechanism shown inFigures l and 2, with the dumping body removed to disclose the systemof levers more clearly.

.Figure 4 isa right-hand end elevation of the dumping body lifting'mechanism shown in Figure 3.

Figure 5 is an enlarged cross-sectional view showing the connection of the lifting mechanism to the dumping body.

In general, the-dump body lifting mechanism of this invention consists of a suitable source of power, such as a hydraulic motor, connected to a plurality of approximately triangular swinging levers. Each lever is pivotally connected at one corner to the motor and at another corner to the truck frame. Each lever also has a longitudinal track forming a'guideway for a roller on the end of another swinging lever pivotally mountedon the frame at a point spaced apart from the pivotal mounting of the triangular lever. The term triangular is used to describe approximately the relative positions of the pivots and track and not the mere outline of the lever itself, which may obviously be of another shape withoutaffecting the operation of the invention. Links connect the ends of the swinging levers with the'dump body in such a manneras to cause the body to be swung upwardly by the hydraulic motor and by the engagement of the triangular levers with the swinging levers. The various lever assemblies are thus analogous to a single set of levers having a fixed length of force arm and avariable length of weight arm, the latterlength increasing. from a minimum at they start of. the lifting operation tov a maximum at. the. close thereof.

Hitherto, dump, body lifting mechanisms have been provided employing .combined linkages, causing the. length of the lever arms to vary abruptly because the point of application of the lifting force is changed abruptly from one point to another during the lifting operation. The present invention, however, utilizes swinging levers to apply a varying mechanical advantage which smoothly and continuously changes without any abrupt changes and Without springs or chains required by the prior art for preventing the body from tilting into too extreme a position. In the present invention a relatively high lifting force is applied to the dump truck at the start of the lifting operation because the weight arm atthis point is relatively short, hence, a relatively low speed of lifting occurs. The length of the weight arm, and consequently the speed .of the lifting, vary continuously and without abrupt changes during the lifting operation until-a relatively low lifting force is applied to the body at the-end of the dumping operation, the

body being then in motion at a comparatively high speed.

Referring to the drawings in detail, Figure 1 shows the longitudinal members H] of a truck frame having a subframe thereon, as shown in Figure 3, the main truck frame in Figure 3 being omitted in order to bring out more clearly the nature of the subframe. The subframe consists of a plurality of cross members |2, l3 and I 4 of angular cross section, interconnected by longitudinal members |5 in such a manner as to form a compact sub-unit. Extending between the cross members HI and I3 are short longitudinal members |6. Pivotally mounted upon the brackets supported by the cross member I3 and adjacent the central longitudinal member I6, is the pivot shaft 8 supporting one end |9 of a hydraulic cylinder 29 having a piston head 2| therein. From the opposite end |9a of the hydraulic cylinder 2|! a piston rod 22 emerges and terminates in a transversely extending crosshead 23.

Passing through the crosshead 23 is a shaft 24, the outer ends of which terminate in sleeves 25 mounted in and extending between the opposite sides of pairs of triangular shaped levers 26. The pivot points of the shaft 24 in the triangular levers 26 are designated 21, these triangular levers being pivotally supported upon pivot shafts 28, which extend between and are supported by triangular brackets 29. The brackets 29 are supported in part by the cross member l2 and in part by the longitudinal members IS. The triangular levers 26 are provided with cross rods 30, arranged to support a trackway 3|. Also mounted upon the triangular levers 26 are inwardly extending ledges 32 secured thereto by the bolts 33. Each pair of triangular levers 26 thus forms a lever unit having a trackway portion 3| and a pair of inwardly extending ledges 32. These provide for the reciprocation of a pair of rollers 34 mounted upon shafts 35 supported near the ends of a pair of swinging levers 36, the opposite ends of which are mounted upon the pivot shafts 31 at the upper corners of the triangular brackets 29 (Figures 1 and 2). The swinging levers 36 are curved roughly in the form of a sickle, the indentation 38 of which serves as a stop to receive the sleeve 25 mounted on the crosshead shaft 24 at the end of the lifting operation.

The outer ends of the curved swinging levers 36 are provided with pivot shafts 39, to which are connected links 40, the opposite ends of which are pivotally attached to the pivot shafts 4| supported by the longitudinal members 42 beneath the truck body 43. The longitudinal members 42 are interconnected by truck body cross members 44 and 45, and a cross member 46 supports the rearward end of the body.' The cross members 44, 45 and 46, in turn, rest upon longitudinal truck body frame members 41, interconnected by suitable cross members (not shown) and having secured thereto the downwardly extending brackets 48. The brackets 48 are provided with a pivot shaft 49, which is supported by the longitudinal subframe members l5 and the cross member H. In order to prevent the centers of the shafts 4|, 39 and 31 from ever getting into a straight-line position, the links 40 are provided with projections 56. These projections also serve as safety stopping points, which engage the levers 36 at 5| and insure the proper return of the body after dumping.

In the operation of the dump body lifting mechanism of this invention, fluid under pressure is admitted to the left-hand end of the hydraulic cylinder 20 (Figure 1), thereby causing the piston rod 22 thereof to move to the right, carrying with it the crosshead 23, the shaft 24 and the sleeves 25 associated therewith. This action swings the triangular levers 26 upwardly to the right in an arcuate path around the pivot shafts 28 as a center. As this occurs the rollers 34 travel upwardly in the guideway formed between the track portion 3| and the ledges 32, thereby causing the left-hand ends of the curved levers 36 to be swung upwardly to the right around the pivot shafts 31 mounted in the triangular brackets 29 (Figures 1 and 2). As a result of this motion the shafts 39 on the outer ends of the curved levers 36 describe an arcuate path and exert an upward push upon the links 46, which in turn, transmit a lifting motion to the shafts 4| mounted on the substructure of the dump body 43. By reason of this application of forces, the dump body 43 and the various levers are lifted into the positions shown in the dotted lines in Figures 1, around the pivot shaft 49. At the extreme upper limit of the lifting operation, as

shown in the dotted lines in Figure 1, the sleeves 25 come to rest in the indentations 38 of the curved levers 36, these acting asstops to limit the upward motion of the mechanism.

When it is desired to lower the truck, fluid is discharged from the rearward end of the hydraulic cylinder 26, the piston 2| and piston rod 22 of which move downwardly to the left, reversing the operation of the lever system from that previously described. As the triangular levers 26 move downwardly toward the left, around their pivot shafts 28, the rollers 34 likewise move downwardly in their guideways, causing the curved levers 36 to swing downwardly and carry with them the dump body 43 by reason of the intermediate connection therewith through the links 40.

From a consideration of the forces and lever arms involved in the operation of this mechanism, it will be seen that the length of the force arm, consisting of the distance between the centers of the shafts 24 and 28, remains fixed and invariable as the triangular levers 26 swing upwardly around the pivot shafts 28. The length of the weight arm, however, consists of the distance between the centers of the shafts 35 and 28 force arm, comprising the distance between the shafts 24 and 28. At the top of the lifting operation, however, the weight arm length greatly exceeds the power arm length. Thus the truck body will be lifted slowly with a comparatively large lifting force at the start of the lifting operation, but will increase in lifting speed as the body rises toward its position of maximum height. While this is occurring the lifting force applied is, of course, correspondingly reduced. During the lifting operation, however, the triangular levers 26 do not move at a uniform speed, but their movement is faster at the start and at the finish than during the middle of the stroke, at which time the line between the centers of the shafts 24 and 28 may be approximately at right angles with the piston rod 22. The action of this mechanism thereby adapts itself to the mechanical conditions under which a load is lifted in a dump body.

As the dump body rises and swings toward the Iportions 3| and ledges 32.

, rear,-under vthe influence of the lifting force; the -:center:of gravity of'itsload moves more and more toward a vertical plane passing through the-pivot shaft!!! of the dumplbody. Q'Underthese conditions the force required to continue to move the -:dump body upwardly is correspondingly lessened sothata higher speed of. lifting may be: accomplished with a given force. The mechanism of .zthe present invention takes advantage ofthese conditions to produce. an'efilcientzarrangement, and requires a lifting motor 01 12; minimum power for thispurpose. As the tilting movement starts, however; the length of-thevweightuarm or -lifting -leve1 starts increasing until the triangular 'levers -25 have reached the full extent of. their movement, at which time the rollers 34 upon the. ends of .th-curved levers36 will have-reachedtheupperv ends of the guideways formed between the track During the l operation of the mechanism, theseledges32 hold the rollers 34, arm 36 and-link. in proper relationship with the track 3| and arms 26, and also prevent the body, when tilted, from pulling away from the lifting mechanism.

The present mechanism, therefore, is especially well adapted for use with dump trucks having unusually large bodies, and adapted to carry loads which are heavier than the loads ordinarily accommodated by such trucks. At the same time, this lifting mechanism will lift such a body to the required angle of 45, 50 or 55 degrees, according to the particular requirements.

It will be understood that it is desired to comprehend within this invention such modifications as come within the scope of the claims and the invention.

Having thus fully described our invention, What we claim as new and desire to secure by Letters Patent, is:

1. In a dump truck, a frame, a dump body pivotally mounted thereon, a pair of levers pivotally mounted on said frame at spaced pivot points, the first of said levers having an elongated guideway and the second lever having means movably engaging said guideway at varying points of engagement along said first lever, means for pivotally connecting said second lever to said dump body, and a source of lifting force connected to said frame and applied to the first of said levers to vary the eflective lifting force during the lifting operation.

2. In a dump truck, a frame, a dump body pivotally mounted thereon, a pair of levers pivotally mounted on said frame at spaced pivot points, the first of said levers having an elongated guideway and the second lever having a roller traveling in said guideway at a varying distance from the pivot point of said guideway-equipped lever, means for pivotally connecting said second lever to said dump body, and a source of lifting force connected to said frame and applied to the first of said levers.

3. In a dump truck, a frame, a dump body pivotally mounted thereon, a pair of levers pivotally mounted on said frame at spaced pivot points, the first of said levers having an elongated guideway and the second lever having a roller traveling in said guideway at a varying distance from the pivot point of said guideway-equipped lever, means for pivotally connecting said second lever to said dump body, and a source of lifting force connected to said frame and applied to the lever having the guideway.

In a dump truck, a frame, a dump body pivotally mounted thereon, a pair of levers pivotally! -mounted .on .-.said: frame l at spaced pivot -,points,;theifirst of saidilevers having an elongated igu-ideway-and the second lever having a roller traveling in said guidewayat a. varyingdistance irfrom :the=.=.pivot.point of said lever, means for ".pivotally connecting said second lever to said -*dump body, .anda source of. lifting force con- -nected-to:.saidframe .and' applied to the lever z-havingithe guideway atv a point remote fromthe fulcrum pointaof said. guideway lever.

=5.'"-In: a dump truck, a frame, a dump body :pivotally mounted thereon, a lever with an elon- :.gated-guideway having its fulcrum mounted on said frame, motor means connected to said frame and operatively connected to another point on said lever, a: second lever pivotally mounted on saldframe at. a p'oint remote from the fulcrum -'oi said"first-lever and toward said dump body pivot-onsaid frame, a follower engaging said guideway and connected to said second lever for;

effecting a sliding engagement between said ieverspand means-for connecting one of said leversto said dump body.

-6. --In-a -dump truck, a' frame, a "dump body pivotally mounted thereon, a lever having its fulcrum mounted on said frame, motor means connected to said frame and operatively connected to another point on said lever, a second lever pivotally mounted on said frame at a point remote from the fulcrum of said first lever and toward said dump body pivot on said frame, said first lever having a guideway and said second lever having a follower for movably engaging said guideway, and means for connecting said second lever to said dump body.

'7. In a dump truck, a frame, a dump body pivotally mounted thereon, a lever having its fulcrum mounted on said frame, motor means connected to said frame and operatively connected to another point on said lever, a second lever pivotally mounted on said frame at a point remote from the fulcrum of said first lever and toward said dump body pivot on said frame, said first lever having a guideway and said second lever having a follower for movably engaging said guideway, and means for connecting said second lever to said dump body at a fixed location thereon.

8. In a dump truck, a frame, a dump body pivotally mounted thereon, a lever having its fulcrum mounted on said frame, motor means connected to said frame and operatively connected to another point on said lever, a. second lever pivotally mounted on said frame at a point remote from the fulcrum of said first lever and toward said dump body pivot on said frame, said first lever having a longitudinal guideway and said second lever having a roller engaging and traveling in said guideway toward and away from the fulcrum of said first lever, and link means for pivotally connecting said second lever to said dump body at a fixed location thereon.

9. In a dump truck, a frame, a dump body pivotally mounted thereon, a lever pivotally mounted on said frame and having its free end operatively connected to said dump body, an approximately triangular lever pivotally mounted on saidframe and having a guideway, motor means mounted on said frame and operatively connected to said triangular lever at a point spaced apart from the fulcrum thereof, and means associated with said first-mentioned lever for movably engaging said guideway whereby to receive and transmit a variable lifting force to said dump truck.

10. In a dump truck, a frame, a dump body pivotally mounted thereon, a lever pivotally mounted on said frame and having its free end operatively connected to said dump body, an approximately triangular lever pivotally mounted on said frame at a point remote from the other lever and having a guideway, motor means mounted on said frame and operatively connected to said triangular lever at a point spaced apart from the fulcrum thereof, and means associated with said first-mentioned lever for movably engaging said guideway whereby to receive and transmit a variable lifting force to said dump truck.

11. In a dump truck, a frame, a dump body pivotally mounted thereon, a lever pivotally mounted on said frame and having its free end operatively connected to said dump body, an approximately triangular lever pivotally mounted on said frame and having a guideway, motor means mounted on said frame and having a cross-head operatively connected to said triangular lever at a point spaced apart from the fulcrum thereof, and means associated with said first-mentioned lever for movably engaging said guideway whereby to receive and transmit a variable lifting force to said dump truck.

12. In a dump truck, a frame, a dump body pivotally mounted on the rear end of the frame, a

lifting motor pivotally mounted on the frame forwardly of the pivotal mounting of said dump body thereon, a plurality of pivotally mounted levers pivotally mounted on spaced pivots on said frame, one of said levers'having an elongatedbody at a fixed location thereon, said bodyconnected lever having a curved portion adapted to provide limiting means for limiting the stroke of said motor-connected lever.

FRED BISZAN'IZ. KENNETH JOSEPH KING. 

